Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!umich!yale!think.com!mck-csc!jw
From: jw@mck-csc.mckinsey.com (Jeffrey Weiss)
Newsgroups: sci.electronics
Subject: Re: Universal IR Remote Receiver
Message-ID: <1990Oct30.224524.21962@mck-csc.mckinsey.com>
Date: 30 Oct 90 22:45:24 GMT
References: <10955@goofy.Apple.COM> <15934@hydra.gatech.EDU>
Reply-To: jw@mck-csc (Jeffrey Weiss)
Organization: McKinsey & Company, Inc., Cambridge, MA
Lines: 25

In article <15934@hydra.gatech.EDU> byron@cc.gatech.edu (Byron A Jeff) writes:
>In article <10955@goofy.Apple.COM> hunter@apple.com (Kurt Hunter) writes:
>-Does anyone know of a discrete or integrated amplifier circuit that can be 
>-used to increase the signal of an IR detector diode while preserving all 
>-the IR signal data? ...
>
>I refer you to the March 1987 issue of BYTE magazine pg. 113. Steve Ciarcia
>Has a design for a trainable master remote controller. Instead of trying
>to do the carrier frequency and pulse detection in analog he samples the
>IR signal at a 1 Mhz rate and uses a microcontroller to examine the sample
>for the carrier and pulse lengths....
>
>He uses a simple LM311 comparator circuit to boost the signal and then 
>shifts the data into a sift register at 1 Mhz....
You will have a problem if you use this method.  Ciarcia's application 
requires that the receiver be about one inch from the transmitter; it's used
to train a multi-remote.  For any reasonable distance, the photo diode or
transistor puts out precious little signal!  The 311 will not do the trick, a
very highly sensitive and low noise pre-amp is required....and as the original
poster identified, commercially available receivers-in-the-can seem to all
include an assumption of a ~40KHz carrier, and remove this carrier for you.
-- 

jw@mckinsey.com (...mit-eddie!mck-csc!jw)
Jeffrey Weiss